This invention is in the field of implements for towing behind a tractor or like towing vehicle, and in particular an apparatus that allows such implements to be towed on a path offset from the tractor.
It is sometimes desirable to tow an implement along a path that is offset from the path of the tractor. An example is where a rotary mower is used to cut a roadside ditch area that slopes downward from the edge of the road. Conventionally the mower follows substantially behind the tractor, requiring the tractor to travel on the slope of the ditch. This travel path can be hazardous where the ditch slope is steep. U.S. Pat. No. 5,957,475 to Pearen et al. discloses an offset hitch for towing an implement, such as a rotary mower. The apparatus comprises a frame with a hitch coupling attached on an arm at the front of one end for attachment to the tractor draw bar hitch, and a draw bar hitch at the rear of the opposite end of the frame for attachment to a mower. The mower is conventional and attached to the draw bar hitch of the apparatus in the same manner as it would be attached to a conventional tractor draw bar hitch.
Ground wheels fixed to the frame define an intended direction of working movement. Towing the mower at the outside end of the frame causes a torque on the frame that tends to move the outside end of the frame back, pivoting about the vertical axis at the tractor draw bar hitch. The ground wheels attached to the frame however are fixed in alignment with the travel direction and resist this torque, maintaining the travel direction.
The hitch and mower assembly can pivot about a vertical yaw axis at the tractor draw bar hitch, in the same manner as any conventional mower. The attachment of the mower to the draw bar hitch at the outside rear of the frame is also conventional such that the assembly can also pivot about a vertical yaw axis at the draw bar hitch at the rear of the apparatus. Thus the wheels on the mower do not resist any lateral torque, and this function is accomplished solely with the fixed ground wheels attached to the frame. Resisting this torque causes considerable side forces on the ground wheels.
The arm at the front of the frame can be pivoted to various positions to vary the amount of offset from a maximum to a minimum transport position. The arm can be pivoted on the go with a hydraulic cylinder, as illustrated in FIG. 2 of the ""457 patent. With the ground wheels fixed, pivoting the arm from one side to the other can increase the side forces on the ground wheels, especially on sloped terrain.
When attempting to back up the apparatus of Pearen et al., the connected assembly of the tractor, frame, and mower can pivot at the tractor draw bar and also at the apparatus draw bar, making it very difficult, if not impossible, to back up the mower. Often when mowing ditch slopes the apparatus will encounter signs or like obstructions, necessitating steering around the obstruction. It would be an advantage to be able to mow close to the obstruction and then back away before moving around it.
Another disadvantage of the apparatus of Pearen et al. is that when the arm at the front of the frame is positioned for transport, as illustrated in FIG. 2 of the ""457 patent, the mower is still in a significantly offset position such that when the tractor is on the road, the mower extends into the ditch, reducing safe transport speeds.
Conventional attachment of a mower should also allow the mower to pivot about a pitch axis oriented horizontal and perpendicular to the operating travel direction and to pivot about a roll axis oriented horizontal and parallel to the operating travel direction, as well as allowing the mower to pivot about the vertical yaw axis. The roll and pitch axes may be provided by a mechanism with pins, bushings and the like, or may simply be provided by a loose fit of the vertical pin attaching the mower to the draw bar hitch. In any event the mower should be able to roll and pitch to a certain extent at least in order to follow ground contours independently of the towing vehicle.
It is an object of the present invention to provide an offset tow arm apparatus for rotary mowers, and like implements having wheels fixed in an operating travel direction, that overcomes disadvantages of the prior art. It is a further object of the present invention to provide such an offset tow arm apparatus that allows the attached implement to be more easily moved in a rearward direction than the apparatuses of the prior art. It is a further object of the present invention to provide such an offset tow arm wherein stress on the wheels supporting the apparatus is reduced.
It is a further object of the present invention to provide an offset tow arm apparatus that comprises a tow arm extending laterally from the implement, and laterally fixed to the implement, and supported on castor wheels so that the tow arm can move freely in any direction, and the direction of the implement and offset hitch is dictated by the wheels supporting the implement.
It is a further object of the present invention to provide an offset rotary mower apparatus that is more easily moved in a rearward direction than the apparatuses of the prior art.
In a first aspect the present invention provides an offset tow arm apparatus for towing an implement in an operating travel direction, where the implement is supported by at least one wheel having a rotational axis substantially perpendicular to the operating travel direction.
The apparatus comprises a tow arm having an inner end adapted for pivotal attachment at a front portion thereof to a towing vehicle hitch such that the tow arm extends laterally from an attached towing vehicle, and such that the tow arm can pivot about a substantially vertical axis, and an outer end. At least one castor wheel is pivotally attached to the tow arm about a substantially vertical castor axis to support the tow arm for movement along the ground in any direction. An implement attachment mechanism is located at an outer portion of the tow arm and is adapted for attachment of an implement to be towed behind the tow arm such that the attached implement is prevented from pivoting about a vertical axis with respect to the tow arm.
The invention provides, in a second aspect, an offset rotary mower apparatus adapted at a front end thereof for attachment to a tractor for movement in an operating travel direction. The apparatus comprises a rotary mower unit supported at a rear end thereof by at least one rear wheel having a rotational axis oriented substantially perpendicular to the operating travel direction. A tow arm extends laterally from a front end of the rotary mower unit such that an inner end of the tow arm is offset from the rotary mower unit, and such that the tow arm is maintained in a substantially fixed lateral position with respect to the rotary mower unit. A pivot arm extends forward from the inner end of the tow arm and has a rear end pivotally attached to the tow arm about a substantially vertical axis, and has a front end adapted for pivotal attachment to a tractor draw bar hitch such that the pivot arm can pivot about a substantially vertical axis. An actuator is operative to selectively pivot the pivot arm with respect to the tow arm, and is operative to maintain the pivot arm in a selected fixed position with respect to the tow arm. An outer castor wheel is pivotally attached to the apparatus about a substantially vertical castor axis to support the outer end of the tow arm for movement along the ground, and an inner castor wheel is pivotally attached to the apparatus about a substantially vertical castor axis to support the inner end of the tow arm for movement along the ground. A driveline is adapted at an inner front end thereof for operative connection to a power output shaft of a tractor and operatively connected at an outer rear end thereof to a power input shaft of the rotary mower unit.
The invention provides, in a third aspect, an offset rotary mower apparatus adapted at a front end thereof for attachment to a tractor for movement in an operating travel direction. The apparatus comprises a rotary mower unit supported at a rear end thereof by at least one rear wheel having a rotational axis oriented substantially perpendicular to the operating travel direction. A tow arm extends laterally from a front end of the rotary mower unit such that an inner end of the tow arm, adapted for attachment to a towing vehicle, is offset from the rotary mower unit. Means are provided to substantially prevent lateral movement of the tow arm with respect to the rotary mower unit. At least one castor wheel is pivotally attached to the apparatus about a substantially vertical castor axis to support the tow arm for movement along the ground in any direction.
The assembled implement and tow arm are fixed laterally with respect to each other, and the offset end of the tow arm is attached to the tow vehicle. The assembly may thus be reversed in much the same manner as any conventional implement, as opposed to prior art systems where the attached assembly includes a second vertical axis, and reversing is difficult.
During operation, through turns and the like, the castor wheels will swivel with minimal resulting side force on the castor wheels. Conventional attachment of many implements requires the tractor to carry considerable weight. When using an offset tow arm apparatus, that weight is carried on the wheels of the apparatus and so can exert considerable stress if the wheels must move laterally without swiveling.